Spiderman would need 43-inch hands to stick to a wall, Cambridge University finds

Only unfeasibly large hands and feet could keep spiderman stuck to a wall, a
Cambridge University has found

Spiderman could never exist because he would need 43 inch hands and size 114 feet to stick to the wall without falling off, Cambridge University has discovered.

In fact the largest animal that is capable of supporting its own weight is a gecko, and for any creature heavier it would be impossible for it to evolve large enough adhesive pads.

The researchers found that as climbing animals grow in weight and size, the body surface needed to be ‘sticky’ increases exponentially.

"There is a maximum size for animals climbing with sticky footpads – and that turns out to be about the size of a gecko.”

Dr David Labonte, Cambridge University

Small creatures like mites and ants are so light that they can cling to surfaces with only small feet But larger animals would require impossibly big feet.

For humans to stick to a wall we would need 80 per cent of our front to be covered in sticky footpads.

“If a human, for example, wanted to climb up a wall the way a gecko does, we’d need impractically large sticky feet – and shoes in European size 145 or US size 114,”says Walter Federle, senior author also from Cambridge’s Department of Zoology.

Spiderman is too heavy to stick to walls, says Cambridge University

Dr David Labonte added: “As animals increase in size, the amount of body surface area per volume decreases – an ant has a lot of surface area and very little volume, and an elephant is mostly volume with not much surface area.

“This poses a problem for larger climbing animals because, when they are bigger and heavier, they need more sticking power, but they have comparatively less body surface available for sticky footpads.

“This implies that there is a maximum size for animals climbing with sticky footpads – and that turns out to be about the size of a gecko.”

The researchers compared the weight and footpad size of 225 climbing animal species including insects, frogs, spiders, lizards and even a mammal.

“We covered a range of more than seven orders of magnitude in body weight, which is roughly the same weight difference as between a cockroach and Big Ben” added Dr Labonte.

“Although we were looking at vastly different animals – a spider and a gecko are about as different as a human is to an ant – their sticky feet are remarkably similar.

“Adhesive pads of climbing animals are a prime example of convergent evolution – where multiple species have independently, through very different evolutionary histories, arrived at the same solution to a problem.

“When this happens, it’s a clear sign that it must be a very good solution.”

There is one other possible solution to the problem of how to stick when you’re a large animal, and that’s to make your sticky footpads even stickier.

“We noticed that within some groups of closely related species pad size was not increasing fast enough to match body size yet these animals could still stick to walls,” said Christofer Clemente, a co-author from the University of the Sunshine Coast.

“We found that tree frogs have switched to this second option of making pads stickier rather than bigger. It’s remarkable that we see two different evolutionary solutions to the problem of getting big and sticking to walls.”

Garfield as Spider-Man Photo: Photoshot

“Across all species the problem is solved by evolving relatively bigger pads, but this does not seem possible within closely related species, probably since the required morphological changes would be too large. Instead within these closely related groups, the pads get stickier in larger animals, but the underlying mechanisms are still unclear. This is a great example of evolutionary constraint and innovation.”

The researchers say that these insights into the size limits of sticky footpads could have profound implications for developing large-scale bio-inspired adhesives, which are currently only effective on very small areas.

“Our study emphasises the importance of scaling for animal adhesion, and scaling is also essential for improving the performance of adhesives over much larger areas.

“There is a lot of interesting work still to be done looking into the strategies that animals use to make their footpads stickier - these would likely have very useful applications in the development of large-scale, powerful yet controllable adhesives,” added Dr Labonte.